header .header_bottom .all_class ul{
  background-color: #555;
  opacity: 0.7;
  display: none;
}
header .header_bottom .all_class h2{
  font-size: 20px;
  background-color: #e05c46;
}
header .header_bottom .nav #home_page{
  border-bottom: none
}
header .header_bottom .nav .prevent_page{
  border-bottom: 3px solid #fff;
}
header .header_bottom .nav #home_page:hover{
  padding-bottom: 2px;
  border-bottom: 3px solid #fff;
}
header .header_bottom .nav .second_sheet:hover{
  padding-bottom: 4px;
  border-bottom: 3px solid #fff;
}

/* section */
section .bg{
  width: 100%;
  margin: 60px 0;
}
section .bg img{
  width: 100%;
}
section h1{
  color: #999;
  text-align: center;
  font-size: 40px;
  font-weight: normal;
}
section .content{
  width: 60%;
  margin: auto;
}
section .content img{
  width: 100%;
}